Physiology Block 3 Week 17 19 Exercise Flashcards Preview

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Flashcards in Physiology Block 3 Week 17 19 Exercise Deck (43)

Essential aspects in mobilization

communication, energy production, and transportation.

a) the brain must stimulate muscles for coordinated contractions

b) fuel must be made available for the energy needed for muscle contractions

c) oxygen must be provided and waste products must be eliminated.


Where do commands for voluntary movement originate from?

Cortical associate areas


What parts of the brain plan voluntary movements?

The cortex, basal ganglia, and cerebellum work cooperatively to plan movements.

Basal ganglia and cerebellum are part of a feedback circuit concerned with planning and organizing voluntary movement


What feedback does the cerebellum provide in movements?

Feedback to adjust and smooth movements


How are movements from the cortex relayed to muscles?

Executed by the motor cortex thru impulses via corticospinal tracts to spinal motor neurons


Supplementary motor area

involved in organizing or planning particularly complex movement.


Premotor area

setting posture at the start of movement or in control of proximal limb muscles needed to orient the body for movement.


How is the complexity of movement distributed amongst the areas of the cortex?

31% of corticospinal tract neurons are from the primary motor cortex

29% from the premotor and supplementary motor cortex

the remaining 40% from neurons in the primary somatic sensory cortex and posterior parietal cortex

This distribution is indicative of the complexity and multiple muscles that need to be activated for coordinated/smooth movements.


Regions of the human cerebral cortex and other areas concerned with control of voluntary movement

Prefrontal Cortex

Premotor Cortex

Supplementary Motor Area

Motor Cortex

Primary Somatic Sensory Cortex

Posterior Parietal Cortex


Damage to cerebellum leads to?

Ataxia and tremors

Cerebellum provides coordinated muscle activity through input from the contracting muscles and then relaying signals to the primary motor cortex


Basal ganglia are composed of several nuclei and three major biochemical pathways that influence the motor cortex via thalamus


Disease of these pathways lead to hyperkietic (Parkinson's) or hypokinetic muscle conditions


How can contractile muscle strength be increased?

Contractile muscle strength
can be increased by increasing muscle size through exercise training programs and through the action of anabolic steroids such as testosterone.


Work performed by muscles

Force applied x distance force applied


Power vs strength

Power is work over period of time


Is power output greater during a 100 m dash or running a mile?

100 m dash

Maximal power out declines with duration of muscle contraction



time a task can be sustained before exhaustion

Determinant of endurance is glycogen stores in muscle from one's diet

High carb diet: high glycogen stores (40 g/Kg)
Mixed diet: 20 g/Kg
High fat: 6g/Kg


Why is ATP a good source of energy?

-The last 2 phosphate bonds are high energy

-Only good for 3 seconds of maximal muscle power

-need continuous supply of ATP



Broken down into creatine and phosphate

Muscles have 2-4x more stored than ATP


Phosophagen Energy System

Phosphocreatine and ATP energy storage

Sufficient to provide E for a power event like 100m dash


Glycogen-Lactic Acid System

Anaerobic Metabolism: If oxygen is not available, pyruvic acid is converted to lactic acid which diffuses out of the muscle.

Maximum muscle activity for about 1.5 minutes

Important at work rates greater than about 60% of maximal oxygen consumption


How are high work rates achieved?

Oxygen consumption is proportional to the work load, but there is a maximal capability to provide energy through the oxidative pathway

High work rates are achieved by large increases in contribution from the lactic acid pathway


Aerobic System

oxidation of foodstuffs in mitochondria where glucose, fatty acids, and amino acids are broken down to release energy and form ATP

Supply energy as long as nutrients are available
--provides for endurance of the muscles.

The oxidative pathway provides 32 ATP molecules/molecule of glucose.

Availability of nutrients is enhanced by increased epinephrine during exercise thereby increasing glucose output from the liver and fatty acid output from adipose tissue.


Relative Moles of ATP generated

Phosphagen System
Glycogen-Lactic Acid System
Aerobic System

Phosphagen System: 4
Glycogen-Lactic Acid System: 2.5
Aerobic System: 1


Oxygen Debt

Oxygen consumption remains elevated after exercise to reconstitute (build up) the phosphagen system and convert lactic acid to glucose.


As work rate increases, what happens to:


VO2, CO, and HR increase linearly until 60% of maximal exercise due to max SV

Thus, further increases in cardiac output are dependent on increases in heart rate


During exercise, what happens to blood pressure and TPR?

Systolic: Large Increases
Diastolic: very small increase
TPR: Dramatic decrease

The increase in systolic pressure and decrease in TPR is from vasodilation increasing flow to the muscles

Rhythmic due to capillary compression during muscle contraction


How does CO (flow) to change from rest to exercise in:


Increased: Muscle

Decreased: Brain, Abdomen, Kidney

Unchanged: Skin and Heart


Exercise Centers

In the cerebral cortex

Increase sympathetic/ dec parasympathetic output to the heart and blood vessels

Increase baroreceptor reflex set point via the medullary cardiovascular nuclei

***symp vasoconstriction to non-exercising vascular beds (GI and Kidneys)

***local vasodilation in muscles


During exercise, how does ventilation change at:

--up to 60% max
--intense exercise
--low work rate

60% max: ventilation increases in proportion to metabolic rate

High intensity exercise: hyperventilation--indicates increasing more than metabolic rate

Low work rate: increased ventilation due to increased tidal volume
--more fresh air to lungs with each breath (decreased dead space: tidal volume)

At high TV, lung compliance decreases
--to increase ventilation, increase breathing frequency


Exercise on arterial blood gases

Signal for hypercapnea not from increased stimulation of carotid and intracranial chemoreceptors

Above 60% max: lacacidosis and hyperventilation


Ventilation (atmospheric to alveolar gas exchange) and Diffusion (alveolar to capillary gas exchange) increases with exercise

The increase in diffusion is due to recruitment of alveolar capillary units which increases the surface area for gas exchange.

The increase in the alveolar-capillary PO2 difference at high workloads = hyperventilation and failure of diffusing capacity to increase by the same amount.

The increase in PAO2 provides increased driving pressure for diffusion of oxygen.


Why is pulmonary capillary dilation important in exercise?

The need for gas exchange is greatly increased since arterial-venous (mixed venous) PO2 difference increases
--Exercise MV PO2 << Rest MV PO2

The pulmonary capillaries will dilate so blood remains in lung for longer duration for more extraction


What causes greater extraction of oxygen during exercise to tissues?

This greater extraction of oxygen during exercise is a result of decreased hemoglobin affinity for oxygen

Increases the driving pressure of oxygen from the capillaries to the tissue

Vasodilation in the muscles causes a greater cardiac output delivered to tissues with a high metabolic rate


How much energy released by ATP during exercise is converted to work?

25%, therefore 75% converted into heat

The body will retain some heat and allow the body temp to increase


Ways to lose heat

Vasodilation of arterioles in the skin

Sweating (increased symp innervation to sweat glands)

Temperature controlled by thermoreceptors in skin (environmental temp) and hypothalamus (body temp)

Hydration and electrolyte balance


Neuroendocrine responses to exercise

Increased GH and cortisol after exercise
--tissue repair

Catecholamines (Epi and NE)
--liver release of glucose and adipose release of fatty acid to maintain ATP (glucagon); suppressed insulin

Opiods (endorphins)
--runner's high


What contributes to increasing maximal oxygen consumption during physical training?

The amount of increase is related to the intensity and duration of the exercise program

Contributing to the increase in maximum oxygen consumption:

-Increased CO secondary to increased in SV and HR

-Enhanced heart performance due to:
--increase muscle and myocyte site
--increased vascularization

Increased vascularization of skeletal muscle:
--enhances delivery of blood
--reduce the distance for gas diffusion between vasculature and muscle

Training enhances endocrine, thermoregulatory, and metabolic responses
--enhance mobilization of glucose and fatty acids
--elimination of heat


Does training enhance the respiratory system?

Other than training of the respiratory muscles, there is little evidence that training enhances the respiratory system.


Limiting Factors to maximal oxygen consumption

Cardiovascular system's capability to deliver oxygen

Capability of muscle to extract oxygen

Respiratory muscles "steal oxygen" from locomotor muscles



Fatigue limiting work performance is a decrease in work capacity due to work itself.

Also induced by (mental) boredom/staleness, drugs, and illness.

8 hours of office work fatigue is different from 8 hours of heavy construction work

Physical fatigue can be due to:
a) depletion of energy stores
b) accumulation of metabolic waste products
c) breakdown of homeostasis

Potential sites of work induced fatigue include the: a) muscle fiber
b) motor nerve and end plate
c) synapses within ganglia
d) the nerve cell body
e) sensory nerve ending

Motivation--limitations to exercise performance are dependent to some extent on tolerating and/or suppress sensations of fatigue and/or pain


Which of the following statements regarding the signal for limb movement during muscular exercise is INCORRECT?

the cerebral cortex, basal ganglia, and cerebellum collaborate to plan the movement.

the signal for the movement is relayed from the brain to the muscles through the corticospinal tract.

the cerebellum provides feedback to the motor cortex to adjust and smooth movement.

the primary motor cortex is the site from which all movement originates.

dopaminergic, cholinergic, and GABAergic systems in the basal ganglia influence the motor cortex through the thalamus.

the primary motor cortex is the site from which all movement originates

Pre-motor, motor, and intermediate cerebellum


A high carbohydrate diet would be most beneficial to which of the following?

An Olympic sprinter running 100 meters.

A weight lifter competing in the Olympics.

An emphysema patient fishing in a trout stream.

A middle-aged man running the Boston marathon.

A farmer with interstitial lung disease driving a tractor.

A middle-aged man running the Boston marathon.


Which of the following would be expected to decrease as a healthy untrained person undergoes an exercise-training program?

Resting stroke volume
Resting cardiac output
Resting heart rate
Maximal oxygen uptake
Maximal alveolar ventilation

Resting heart rate